Hydroxylic acrylate copolymer process for its preparation, and coating agent based on the acrylate

ABSTRACT

The invention relates to a hydroxylic acrylate copolymer which contains a proportion of copolymerized monomers having at least 2 double bonds, and to the process for the preparation of the acrylate copolymer. The invention also relates to coating agents which contains acid-curable binders, organic solvents and, if appropriate, pigments, fillers and conventional assistants and additives and which contain, as the essential binder, the hydroxylic acrylate copolymer and an alkylated melamine/formaldehyde resin. The invention also relates to coating agents which, as the essential binders, contain the hydroxylic acrylate copolymer in one or more different polyfunctional isocyanates.

The application is a continuation of application Ser. No. 813,276 filedDec. 4, 1985, now abandoned.

The invention relates to a hydroxylic acrylate copolymer produced bycopolymerization of acrylates having at least 2 olefinically unsaturated(sic) double bonds, hydroxylic monomers and further olefinicallyunsaturated monomers.

EP-A No. 103,199 has disclosed an acrylate copolymer of theabovementioned type. EP-A No. 103,199 has also disclosed the processingof the copolymer of the abovementioned type with a suitable crosslinkingagent to give a coating agent. An etherified amine/formaldehyde resin ismentioned inter alia as a crosslinking agent.

Moreover, EP-A No. 64,338 has disclosed an acid-curable coating agentbased on an acrylate copolymer and a melamine/formaldehyde resin.

It is the object of the present invention to provide a crosslinkableacrylate copolymer and coating agents which are based on thecrosslinkable acrylate copolymer and have an improved fastness togasoline and an improved resistance to long-term exposure to water orsteam.

The object is achieved by a hydroxylic acrylate copolymer of theabovementioned type, which has been obtained from

(a₁) 10 to 60% by weight, preferably 15 to 60% by weight, of hydroxylicesters of acrylic/methacrylic acid, having 2 to 14 carbon atoms in thealkali radical,

(a₂) 3 to 25% by weight, preferably 5 to 20% by weight, of monomershaving at least 2 polymerizable olefinically unsaturated (sic) doublebonds, and

(a₃) 15 to 82% by weight, preferable 40 to 70% by weight, of furtherpolymerizable monomers having one olefinically unsaturated (sic) doublebond, the sum of components a₁, a₂ and a₃ being 100% by weight.

Compounds of the general formula ##STR1## where R=H or CH₃,

X=O, N or S

n=2 to 8,

can advantageously be used as the component a₂.

Examples of such compounds are hexanediol diacrylate, hexanedioldimethacrylate, glycol diacrylate, glycol dimethacrylate, butanedioldiacrylate, butanediol dimethacrylate and similar compounds.

The component a₂ can advantageously also be a reaction product of acarboxylic acid having a polymerizable olefinically unsaturated (sic)double bond and glycidyl acrylate and/or glycidylmethacrylate, or apolycarboxylic acid or unsaturated monocarboxylic acid esterified withan unsaturated alcohol.

Moreover, the component a₂ can advantageously be a reaction product of apolyisocyanate and an unsaturated alcohol or amine. The reaction productof one mol of hexamethylene diisocyanate and 2 mol of allyl alcohol maybe mentioned as an example.

Another advantageous component a₂ is a diester of polyethylene glycoland/or polypropylene glycol of a mean molecular weight of less than1500, preferably less than 1000, and acrylic and/or methacrylic acid.According to the invention, acrylates having more than 2 ethylenicallyunsaturated (sic) double bonds, for example trimethylolpropanetriacrylate or trimethylolpropane trimethacrylate, can also be used asthe component a₂. Of course, combinations of these polyunsaturatedmonomers can also be used.

The component a₁ can especially be a hydroxyalkyl ester of acrylicand/or methacrylic acid, having a primary hydroxyl group, for examplehydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate,hydroxyamyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate andthe corresponding methacrylates.

Advantageously, the component a₁ can at least partially be a reactionproduct of one mol of hydroxyethyl acrylate and/or hydroxyethylmethacrylate and, on average, 2 mol of ε-caprolactone.

Advantageously, up to 75% by weight, and particularly preferably up to50% by weight, of the component a₁ can also be a hydroxylic acrylicand/or methacrylic acid ester with a secondary hydroxyl group, inparticular a reaction product of acrylic and/or methacrylic acid and theglycidyl ester of a carboxylic acid having a tertiary α-carbon atom.2-Hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutylacrylate and the corresponding methacrylates may be mentioned asexamples.

The choice of the further polymerizable monomers of component a₃ is notparticularly critical. These can be chosen from the group comprisingstyrene, vinyltoluene, acrylic acid, methacrylic acid, alkyl esters ofacrylic and methacrylic acid, alkoxyethyl acrylates and aryloxyethylacrylates and the corresponding methacrylates, and the esters of maleicand fumaric acids. Examples of these are methyl acrylate, ethylacrylate, propyl acrylate, butyl acrylate, ssopropyl acrylate, isobutylacrylate, pentyl acrylate, isoamyl acrylate, hexyl acrylate,2-ethylhexyl acrylate, octyl acrylate, 3,5,5-trimethylhexyl acrylate,decyl acrylate, dodecyl acrylate, hexadecyl acrylate, octadecylacrylate, octadecenyl acrylate, pentyl methacrylate, isoamylmethacrylate, hexyl methacrylate, 2-ethylbutyl methacrylate, octylmethacrylate, 3,5,5-trimethylhexyl methacrylate, decyl methacrylate,dodecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate,alkoxyethyl acrylates or methacrylates, such as butoxyethyl acrylate orbutoxyethyl methacrylate, methyl methacrylate, ethyl methacrylate,propyl methacrylate, isopropyl methacrylate, butyl methacrylate,cyclohexyl acrylate, cyclohexyl methacrylate, acrylonitrile,methacrylonitrile, vinyl acetate, vinyl chloride and phenoxyethylacrylate. Other monomers can be used, unless they cause undesirableproperties of the copolymer.

The invention also relates to a process for the preparation of anacrylate copolymer as claimed in any of claims 1 to 11, which comprisescopolymerizing, for its preparation,

(a₁) 10 to 60% by weight, preferably 15 to 60% by weight, of hydroxylicesters of acrylic and/or methacrylic acid, having 2 to 14 carbon atomsin the alkyl radical,

(a₂) 3 to 25% by weight, preferably 5 to 20% by weight, of monomershaving at least 2 polymerizable olefinically unsaturated (sic) doublebonds and

(a₃) 15 to 82% by weight, preferably 40 to 70% by weight, of furtherpolymerizable monomers having one olefinically unsaturated (sic) doublebond, in an organic solvent with the addition of polymerizationinitiators and polymerization regulators to give a precrosslinked,ungelled product, the sum of the components a_(a), a₂ and a₃ being 100%by weight.

Care must be taken in order to obtain a precrosslinked, but ungelledcopolymer. Surprisingly, a clear, transparent, ungelled solution of abranched copolymer can be prepared by means of suitable polymerizationconditions. The use of monomers having at least 2 ethylenicallyunsaturated groups causes precrosslinking of the copolymer molecules,but due to the special reaction conditions according to the inventionthis nevertheless does not lead to gelled products. These specialreaction conditions comprise carrying out the polymerization attemperatures from 80° to 130° C., preferably 90° to 120° C., at arelatively low polymerized solids content of about 50% by weight.Furthermore, it is necessary to use suitable initiators and, dependingon the proportion of difunctional monomer, at least 0.5% by weight, butpreferably at least 2.5% by weight, of a polymerization regulator (chainstopper), for example mercapto compounds. The choice of the initiatordepends on the proportion of the difunctional monomers used. In the caseof a low proportion, the initiators conventional for such temperatures,for example peroxy esters, can be used. In the case of a higherproportion of difunctional monomer, initiators such as azo compounds arepreferably employed. After the polymerization, the polymer solution isconcentrated to the desired solids content, preferably solids contentsof 60% by weight, by distilling off the solvent. When adjusted to asolids content of 50% by weight, the clear copolymer solutions thusobtained have a viscosity of 0.4 to 10 dPas.

Surprisingly, measurements on the acrylate copolymer solutions by meansof photon-correlation spectroscopy do not indicate any microgel content.

The invention also relates to a coating agent which contains a binder,organic solvents, if appropriate pigments, fillers and conventionalassistants and additives and, if appropriate, is curable by means of acatalyst and which, as the essential binder, contains the acrylatecopolymer according to the invention as claimed in one or more of claims1 to 11 and a binder suitable for cross-linking the former.

The invention relates to a coating agent which is curable by means ofacid and, as the essential binder, contains

(A) 55 to 90% by weight, preferably 70 to 80% by weight, of the acrylatecopolymer according to the invention and

(B) 10 to 45% by weight, preferably 20 to 30% by weight, of amelamine/formaldehyde resin having a mean molecular weight from 250 to1000 and a degree of a methylolation of at least 0.65, preferably 0.9 to1, which resin is etherified with monoalcohols having 1 to 4 carbonatoms and/or monoethers of diols having 2 to 7 carbon atoms in total, toan extent of at least 80 mol %, preferably 90 to 100 mol %, based on themaximum possible etherification, the sum of the binders (A) and (B)being 100% by weight.

Preferably, 25 to 40% by weight of the component a₁ is used, the sum ofcomponents a₁, a₂ and a₃ being 100% by weight.

The melamine/formaldehyde resin used as the binder (B) can have beenetherified with, for example, methanol, ethanol, propanol and butanol.Hexakis-(methoxy)-methylmelamine is very suitable. Of course, thecomponent B can also consist of urea/formaldehyde and benzoguanamineformaldehyde resins.

Before they are used, the coating agents according to the invention aremixed with an acid catalyst, in order to reduce the curing temperatureand to accelerate curing. The catalyst is used in a quantity of 1 to 5%by weight, preferably 1.5 to 3.5% by weight, based on the solids contentof binders (A) and (B). Sulfonic acid compounds, in particular p-toluenesulfonic acid, are particularly suitable. Mixtures of catalysts can alsobe employed.

To extend the pot life to 6 to 24 hours after the addition of thecatalyst, the coating agent advantageously contains a quantity of anitrogen-containing compound, equivalent to the quantity of acid, or apart of this quantity, depending on the desired extension of the potlife.

An extension of the pot life can advantageously also be obtained by anaddition of 5 to 35% by weight, based on the solids content of binder,of one or more alcohols, of which ethanol, butanol and mixtures thereofare preferred.

The invention also relates to a process for the preparation of anacid-curable coating agent, which comprises copolymerizing, for thepreparation of an hydroxylic acrylate copolymer,

(A)

(a₁) 10 to 60% by weight, preferably 15 to 60% by weight, of hydroxylicesters of acrylic and/or methacrylic acid, having 2 to 14 carbon atomsin the alkyl radical,

(a₂) 3 to 25% by weight, preferably 5 to 20% by weight, of monomershaving at least 2 polymerizable olefinically unsaturated (sic) doublebonds and

(a₃) 15 to 82% by weight, preferably 40 to 70% by weight, of furtherpolymerizable monomers having one olefinically unsaturated (sic) doublebond, in an organic solvent with the addition of polymerizationinitiators and polymerization regulators to give a precross-linked,ungelled product, the sum of the components a₁, a₂ and a₃ being 100% byweight, and processing this copolymer (A) in a proportion of 55 to 90%by weight, preferably 70 to 80% by weight, with

(B) 10 to 45% by weight, preferably 20 to 30% by weight, of amelamine/formaldehyde resin having a molecular weight from 250 to 1000and a degree of methylolation of at least 0.65, preferably 0.9 to 1,which resin is etherified with monoalcohols of 1 to 4 carbon atomsand/or monoethers of diols having 2 to 7 carbon atoms in total, to anextent of at least 80 mol %, preferably 90 to 100 mol %, based on themaximum possible etherification, and with organic solvents and, ifappropriate, pigments and conventional assistants and additives, bymixing and, if necessary, dispersing to give a coating composition, thesum of binders (A) and (B) being 100% by weight.

The invention also relates to a coating agent which, as the essentialbinder, contains the acrylate copolymer

(A) according to the invention and

(B) one or more different polyfunctional isocyanates, with the provisothat the ratio of the isocyanate groups and hydroxyl groups is withinthe range from 0.3:1 to 3.5:1.

Examples of polyfunctional isocyanates, which can be used forcrosslinking the hydroxylic copolymers, are 2,4-toluylene diisocyanate,2,6-toluylene diisocyanate, 4,4'-diphenylmethane diisocyanate,hexamethylene diisocyanate,3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane, m-xylylenediisocyanate, p-xylylene diisocyanate, tetramethylene diisocyanate,cyclohexane-1,4-diisocyanate, 4,4'-diisocyanatodiphenyl ether,2,4,6-triisocyanatotoluene and 4,4',4"-triisocyanatotriphenylmethane.The polyisocyanates can be linked to give prepolymers of highermolecular weight. Adducts of toluylene diisocyanate andtrimethylolpropane, a biuret formed from 3 molecules of hexamethylenediisocyanate, and the trimers of hexamethylene diisocyanate and3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane may bementioned here.

In the case of the acrylate copolymers crosslinked with isocyanategroups, preferably 15 to 40% by weight of component a₁ are used, the sumof components a₁, a_(b) and a₃ being 100% by weight.

The invention also relates to a process for the preparation of thecoating agent, which comprises copolymerizing, for the preparation ofthe acrylate copolymer,

(A)

(a₁) 10 to 60% by weight, preferably 15 to 60% by weight, of hydroxylicesters of acrylic and/or methacrylic acid, having 2 to 14 carbon atomsin the alkyl radical,

(a₂) 3 to 25% by weight, preferably 5 to 20% by weight, of monomershaving at least 2 polymerizable olefinically unsaturated (sic) doublebonds and

(a₃) 15 to 82% by weight, preferably 40 to 70% by weight, of furtherpolymerizable monomers having one olefinically unsaturated (sic) doublebond, in an organic solvent with the addition of polymerizationinitiators and polymerization regulators to give a pre-crosslinked,ungelled product, the sum of components a₁, a₂ and a₃ being 100% byweight, and processing this copolymer (A) with

(B) one or more different polyfunctional isocyanates and with organicsolvents and, if appropriate, pigments and conventional assistants andadditives, by mixing and, if necessary, dispersing to give a coatingcomposition, with the proviso that the ratio of the isocyanate groupsand hydroxyl groups is within the range from 0.3:1 to 3.5:1.

In the process according to the invention, one or more catalysts in aquantity of 0.01 to 1% by weight, based on the solids content of thereacting components, can be used. The preferred catalysts used areamines, for example dimethylethanolamine. When catalysts are added thecuring temperature can be reduced and curing can be accelerated. Theisocyanate curing according to the invention can be carried out attemperatures as low as room temperature. At very high temperatures, theaddition of a catalyst is unnecessary.

The coating agents according to the invention can be cured at lowtemperatures, for example at 20° to 80° C., and are therefore employedparticularly for automobile finish repairs.

The invention also relates to a process for the preparation of acoating, wherein an acid catalyst in a quantity of 1 to 5% by weight,preferably 1.5 to 3.5% by weight, based on the solids content of binders(A) and (B), is admixed to a coating agent as claimed in claim 18 or 19,the mixture obtained is applied in the form of a film to a substrate byspraying, flooding, dipping, rolling, knife application or brushing anda film is cured at temperatures from 20° to 80° C. to give a firmlyadhering coating.

The invention also relates to a process for the preparation of acoating, wherein a coating agent crosslinked in claim 21 or 22, to whicha catalyst may have been admixed, is applied in the form of a film to asubstrate by spraying, flooding, dipping, rolling, knife application orbrushing and the film is cured to give a firmly adhering coating. Theinvention also relates to substrates coated by a process according tothe invention.

The invention is explained in more detail below by reference toillustrative embodiments.

(A) Preparation of copolymers according to the invention (Binder A)

In the examples which follow, all percentage figures relate to parts byweight, unless otherwise stated. The solids content values weredetermined in a circulating-air oven after 1 hour at 130° C. Theviscosities were determined in a cone-and-plate viscometer.

1 Preparation of acrylate resin I

360 parts of butyl acetate and 180 parts of methoxypropyl acetate areintroduced into a 3 l kettle.

The solvent mixture is heated to 110° C. Within 3 hours, the followingare metered in uniformly:

Solution 1:

300 parts of methyl methacrylate

250 parts of styrene

150 parts of hexanediol diacrylate

250 parts of butanediol monoacrylate

50 parts of n-butyl acrylate

45 parts of mercaptoethanol

Solution 2:

350 parts of butyl acetate

30 parts of azobisisobutyronitrile

175 parts of methoxypropyl acetate

The polymerization is then completed during a further 3 hours at 110° C.A solids content of 50.5% is reached. About 340 parts of solvent aredistilled off in vacuo at 60°-70° C. The clear, colorless acrylate resinsolution has a solids content of 60.6%, an acid number of 0.1, an OHnumber of 97 and a viscosity of 2.0 dPas at 23° C. at a solids contentadjusted to 50% with ethylglycol acetate.

2 Preparation of acrylate resin II

360 parts of butyl acetate and 180 parts of methoxypropyl acetate areintroduced into a 3 l kettle.

The solvent mixture is heated to 110° C. Within 3 hours, the followingare metered in uniformly:

Solution 1:

300 parts of methyl methacrylate

150 parts of styrene

150 parts of hexanediol diacrylate

400 parts of hydroxyethyl methacrylate

45 parts of mercaptoethanol

Solution 2:

350 parts of butyl acetate

30 parts of azobisisobutyronitrile

175 parts of methoxypropyl acetate.

The polymerization is then completed during a further 3 hours at 110° C.A solids content of 50.5% is reached. About 340 parts of solvent aredistilled off in vacuo at 60°-70° C. The clear, colorless acrylate resinsolution has a solids content of 61.4%, an acid number of 0.4, and an OHnumber of 173 and a viscosity of 6.6 dPas at 23° C. at a solids contentadjusted to 50% with ethyl glycol acetate.

3. Preparation of acrylate resin III

360 parts of butyl acetate and 180 parts of methoxypropyl acetate areintroduced into a 3 l kettle.

The solvent mixture is heated to 110° C. Within 3 hours, the followingare metered in uniformly:

Solution 1:

300 parts of methyl methacrylate

150 parts of styrene

150 parts of hexanediol diacrylate

150 parts of hydroxyethyl methacrylate

250 parts of butanediol monoacrylate

45 parts of mercaptoethanol

Solution 2.

350 parts of butyl acetate

30 parts of azobisisobutyronitrile

175 parts of methoxypropyl acetate (sic).

The polymerization is then completed during a further 3 hours at 110° C.A solids content of 49.8% is reached. About 340 parts of solvent aredistilled off in vacuo at 60°-70° C. The clear, colorless acrylate resinsolution has a solids content of 60.9%, an acid number of 0.3, and an OHnumber of 162 and a viscosity of 3.8 dPas at 23° C. at a solids contentadjusted to 50% with ethylglycol acetate.

4. Preparation of acrylate resin IV

240 parts of butyl acetate, 120 parts of methoxypropyl acetate and 10parts of tert.-butylperoxy 2-ethylhexanoate are introduced into a 3 lkettle.

The solvent mixture and a part of the required quantity of initiator areheated to 110° C. Within 3 hours, the following are metered inuniformly:

Solution 1:

300 parts of methyl methacrylate

250 parts of styrene

75 parts of hexanediol diacrylate

75 parts of hydroxyethyl methacrylate

250 parts of butanediol monoacrylate

50 parts of n-butyl acrylate

35 parts of mercaptoethanol

Within 3.5 hours, the following are metered in uniformly:

Solution 2:

240 parts of butyl acetate

35 parts of tert.-butylperoxy 2-ethylhexanoate

120 parts of methoxypropyl acetate.

The polymerization is then completed during a further 3 hours at 110° C.The clear, colorless acrylate resin solution has a solids content of61.5%, an acid number of 4.1, and an OH number of 130 and a viscosity of4.8 dPas at 23° C. at a solids content adjusted to 50% with ethylglycolacetate

5. Preparation of acrylate resin V

360 parts of of butyl acetate, 180 parts of methoxypropyl acetate and 10parts of tert.-butylperoxy 2-ethylhexanoate are introduced into a 3 lkettle.

The solvent mixture is heated to 110° C. Within 3 hours, the followingare metered in uniformly:

Solution 1:

300 parts of methyl methacrylate

250 parts of styrene

75 parts of hexamethylene-bis-methacrylamide

75 parts of hydroxyethyl methacrylate

250 parts of butanediol monoacrylate

50 parts of n-butyl acrylate

35 parts of mercaptoethanol

Within 3.5 hours, the following are metered in uniformly:

Solution 2:

350 parts of butyl acetate

35 parts of tert.-butylperoxy 2-ethylhexanoate

175 parts of methoxypropyl acetate

The polmerization is then completed during a further 3 hours at 110° C.The solids content of 50.9% is reached. About 340 parts of solvent aredistilled off in vacuo at 60°-70° C. The clear, colorless acrylate resinsolution has a solids content of 61.5%, an acid number of 3.1, an OHnumber of 130 and a viscosity of 3.6 dPas at 23° C. at a solids contentadjusted to 50% with ethylglycol acetate.

6. Preparation of acrylate resin VI

361 parts of butyl acetate and 181 parts of ethylglycol acetate areintroduced into a 3 l kettle.

The solvent mixture is heated to 110° C. Within 3 hours, the followingare metered in uniformly:

Solution 1:

300 parts of methyl methacrylate

250 parts of styrene

150 parts of ethylene glycol dimethacrylate

250 parts of butanediol monoacrylate

50 parts of n-butyl acrylate

45 parts of mercaptoethanol

Solution 2:

350 parts of butyl acetate

30 parts of azobisiobutyronitrile (sic)

175 parts of ethyl glycol acetate.

The polymerization is then completed during a further 3 hours at 110° C.A solids content of 48.9% is reached. About 340 parts of solvent aredistilled off in vacuo at 60°-70° C. The clear, colorless acrylate resinsolution has a solids content of 59.1%, an acid number of 1.6, an OHnumber of 97 and a viscosity of 6.5 dPas at 23° C. at a solids contentadjusted to 50% with ethylglycol acetate.

7. Preparation of acrylate resin VII

361 parts of butyl acetate and 181 parts of ethyl glycol acetate areintroduced into a 3 l kettle. The solvent mixture is heated to 110° C.Within 3 hours, the following are metered in uniformly:

Solution 1:

300 parts of methyl methacrylate

150 parts of styrene

150 parts of hexanediol diacrylate

250 parts of butanediol monoacrylate

150 parts of a 1 : 2 reaction product of 2-hydroxyethyl acrylate andcaprolactone, as described below

45 parts of mercaptoethanol

Solution 2:

350 parts of butyl acetate

30 parts of ethylglycol acetate

175 parts of ethylglycol acetate

The polymerization is then completed during a further 3 hours at 110° C.A solids content of 50.3% is reached. About 340 parts of solvent aredistilled off in vacuo at 60°-70° C. The clear, colorless acrylate resinsolution has a solids content of 60.1%, an acid number of 0.7, an OHnumber of 122 and a viscosity of 7.4 dPas at 23° C. originally and aviscosity of 2.2 dPas at a solids content adjusted to 50% withethylglycol acetate.

Reaction product of 2-hydroxyethyl acrylate and caprolactone

A commercially available reaction product, prepared from one mol ofhydroxyethyl acrylate and, on average, 2 mol of ε-caprolactone, wasused.

(B) Preparation of tinting pastes for pigmented top coats

White tinting paste P1

    ______________________________________                                        Acrylate resin I         32.0    parts                                        Titanium dioxide, rutile 53.0    parts                                        Anti-settling agent                                                           (Salt of a higher-molecular polycarboxylic                                                             1.0     part                                         acid, 52% in higher-boiling aromatics)                                        Xylene                   4.3     parts                                        Solvent mixture          6.7     parts                                        (6:4 xylene/butyl acetate)                                                    Treated montmorrillonite 2.0     parts                                        (10% in solvent naphtha/propylene carbonate/                                  soya lecithin 85:4:1)                                                         Pyrogenic silica         1.0     part                                                                  100.0   parts                                        ______________________________________                                    

The items are successively stirred up in a dissolver and then dispersedfor 20 minutes in a commercially available laboratory sand mill (10 μmfineness)

Yellow tinting paste P2

    ______________________________________                                        Acrylate resin I         67.3    parts                                        Anthrapyrimidine yellow (CI Y 108, 68,420)                                                             15.0    parts                                        Solvent mixture          15.0    parts                                        (6:4 xylene/butyl acetate)                                                    Triethylenetetramine     0.2     part                                         Xylene                   2.5     parts                                                                 100.0   parts                                        ______________________________________                                    

The items are stirred up successively in a dissolver and then dispersedfor 60 minutes in a commercially available laboratory and sand mill (10μm fineness).

White tinting paste P3 with extraneous binder

    ______________________________________                                        Solvent mixture (xylene/butyl acetate)                                                                 5.4     parts                                        Commercially available OH-copolymer,                                                                   31.1    parts                                        OH number 150 based on solids, 60% in 2:1                                     xylene/ethylglycol acetate, viscosity                                         (50% in xylene) 450-750 mPas                                                  Anti-settling agent      1.0     part                                         (Salt of a higher-molecular polycarboxylic                                    acid, 52% in higher-boiling aromatics)                                        Treated montmorrillonite 2.0     parts                                        (10% in solvent naphtha/propylene carbonate                                   soya lecithin 85:4:1)                                                         Pyrogenic silica         0.5     part                                         Titanium oxide, rutile   60.0    parts                                                                 100.0   parts                                        ______________________________________                                    

The items are stirred up successively in the dissolver and thendispersed for 20 minutes in a commercially available laboratory sandmill (10 μM fineness).

Green tinting paste

    ______________________________________                                        Acrylate resin I        38.6   parts                                          Titanium dioxide, rutile                                                                              10.7   parts                                          Yellow pigment (Y34, C.I. 77,603)                                                                     4.2    parts                                          Yellow pigment (Y34, C.I. 77,600)                                                                     10.5   parts                                          Green pigment (G7, C.I. 74,260)                                                                       0.5    parts                                          Butanol                 23.2   parts                                          Tetraline               4.6    parts                                          Butyl acetate           7.7    parts                                                                  100.0  parts                                          ______________________________________                                    

The items are stirred up successively in a dissolver and then dispersedfor 20 minutes in a commercially available laboratory sand mill (10 μmfineness).

Red tinting paste

    ______________________________________                                        Acrylate resin I           46.3   parts                                       Red pigment (R104, C.I. 77,605)                                                                          44.2   parts                                       Wetting and dispersing additive                                                                          1.0    part                                        (Partial amide and ammonium salt of a higher-                                 molecular unsaturated polycarboxylic acid, combined                           with an organically modified siloxane copolymer)                              Ethylglycol acetate        8.5    parts                                                                  100.0  parts                                       ______________________________________                                    

The items are stirred up successively in a dissolver and then dispersedfor 20 minutes in a commerically available laboratory sand mill (10 μmfineness).

(C) Preparation of top coats

In the examples which follow, testing of the coatings is carried out asfollows:

The pendulum hardness is determined by the Konig method.

Resistance to premium gasoline (FAM standard gasoline DIN 51,604) andxylene

A small cellulose sheet (diameter about 35 mm) impregnated with theparticular solvent is placed for the indicated time upon the coating(knife-coated on glass in the viscosity as obtained) and covered. Thefilm is examined for softening and marking.

Damp heat resistance

A phosphated steel sheet with the conventional structure (cathodicelectrocoat primer, epoxy filler, top coat) is exposed for the indicatedperiod to a humidity-saturated atmosphere at 40° C.

After one hour of regeneration time, the test sheet is examined forblisters and loss of gloss.

Sticking test

One hour after forced drying of the coating, a strip of crepe adhesivetape is stuck on, firmly pressed on and left for one hour. After theadhesive tape has been torn off, the coating is examined for markings.

EXAMPLE 1

Formulation of a white top coat

    ______________________________________                                        Acrylate resin I          43.5 parts                                          White tinting paste P1    34.3 parts                                          Hexakis-(methoxymethyl)-melamine                                                                         7.7 parts                                          Xylene                    13.8 parts                                          Commercially available silicone oil (5%)                                                                 1.0 part                                           Pyridine salt of p-toluenesulfonic acid                                       (20%)                      5.7 parts                                          ______________________________________                                    

Adjustment diluent: xylene (18 sec DIN 4)

EXAMPLE 2

Formulation of a yellow top coat

    ______________________________________                                        Acrylate resin I          69.1 parts                                          Yellow tinting paste P2   14.0 parts                                          Hexakis-(methoxymethyl)-melamine                                                                        12.0 parts                                          Xylene                     4.9 parts                                          Commercially available silicone oil (5%)                                                                 1.0 part                                           Pyridine salt of p-tolulenesulfonic acid                                      (20%)                      8.5 parts                                          ______________________________________                                    

Adjustment diluent

xylene (18 sec DIN 4)

With forced drying (30 minutes at 60° C.), the following property levelis reached (unless otherwise stated, the exposure tests were carried outone hour after removal from the drying oven).

    ______________________________________                                                         White coat                                                                             Yellow coat                                         ______________________________________                                        Layer thickness     35 μm  33 μm                                        Pendulum hardness 1 hour after                                                                    55 sec    50 sec                                          drying                                                                        After 48 hours     108 sec    97 sec                                          Resistance to a premium                                                                          no marking no marking                                      gasoline and xylene (duration after 24 hrs                                    of exposure 5 minutes in each                                                                    no softening                                                                             no softening                                    case)                                                                         Sticking test (1 hour stressed                                                                   no marking no marking                                      with adhesive tape)                                                           ______________________________________                                    

EXAMPLE 3

Formulation of a white top coat

    ______________________________________                                        Acrylate resin II         36.8 parts                                          Hexakis-(methoxymethyl)-melamine                                                                         7.3 parts                                          White tinting paste P3    29.4 parts                                          Butyl acetate              7.6 parts                                          Butanol                   15.0 parts                                          Commercially available silicone oil (5%)                                                                 1.0 part                                           p-toluenesulfonic acid (40%)                                                                             2.9 parts                                          ______________________________________                                    

Adjustment diluent

methoxypyropyl acetate (18 sec DIN 4)

With forced drying (30 minutes at 60° C.), the following property levelis reached (unless otherwise stated, the exposure tests were carried out1 hour after removal from the drying oven).

    ______________________________________                                        Layer thickness           32 μm                                            Pendulum hardness 1 hour after drying                                                                   95 sec                                              after 48 hours           111 sec                                              Resistance to premium gasoline and xylene                                                              no marking,                                          (duration of exposure 5 minutes in each case)                                                          no softening                                         Sticking test (1 hour stressed with adhesive                                                           no marking                                           tape)                                                                         ______________________________________                                    

With drying at 20° C. (room temperature), the following property levelis reached:

    ______________________________________                                        Resistance to premium gasoline and xylene                                                             no marking,                                           after 3 days (duration of exposure 5 minutes                                                          no softening                                          in each case)                                                                 Exposure to damp heat, 260 hours at 40° C.                                                     no blisters,                                                                  good gloss                                                                    retention                                             ______________________________________                                    

EXAMPLE 4

Formulation of a white top coat

    ______________________________________                                        Acrylate resin III       39.4   parts                                         Hexakis-(methoxymethyl)-melamine                                                                       7.4    parts                                         White tinting paste P3   29.4   parts                                         Methoxypropyl acetate    3.0    parts                                         Butanol                  15.0   parts                                         Tetraline                3.0    parts                                         Commercially available silicone oil (5%)                                                               1.0    part                                          p-toluenesulfonic acid (40%)                                                                           1.8    part                                          ______________________________________                                    

Adjustment diluent

methoxypropyl acetate (18 sec DIN 4)

With forced drying (30 minutes at 60° C.), the following property levelis reached (unless otherwise stated, the exposure tests were carried out1 hour after removal from the drying oven).

    ______________________________________                                        Layer thickness           35 μm                                            Pendulum hardness 1 hour after drying                                                                   91 sec                                              after 4 days             126 sec                                              Resistance to premium gasoline and xylene                                                              no marking,                                          (duration of exposure 5 minutes in each case)                                                          no softening                                         ______________________________________                                    

With drying at 20° C. (room temperature), the following property levelis reached:

    ______________________________________                                        Layer thickness         33 μm                                              Pendulum hardness after 48 hours                                                                      81 sec                                                After 24 hours: resistance to premium                                                                 no marking,                                           gasoline                no softening                                          Resistance to xylene    slight mark-                                          (5 minutes exposure in each case)                                                                     ing                                                   After 48 hours          no marking,                                           Resistance to premium gasoline                                                                        no softening                                          Resistance to xylene    no marking,                                                                   no softening                                          Exposure to damp heat, 260 hours at 40° C.                                                     no blisters,                                                                  slight dulling                                        ______________________________________                                    

EXAMPLE 5

Formulation of a white top coat

    ______________________________________                                        Acrylate resin IV         39.7 parts                                          Hexakis-(methoxymethyl)-melamine                                                                         7.3 parts                                          White tinting paste P3    29.4 parts                                          Butyl acetate              4.8 parts                                          Butanol                   15.0 parts                                          Commercially available silicone oil (5%)                                                                 1.0 part                                           p-toluenesulfonic acid (40%)                                                                             2.8 parts                                          ______________________________________                                    

Adjustment diluent

xylene (18 sec DIN 4)

With forced drying (30 minutes at 60° C.), the following product levelis reached (unless otherwise stated, the exposure tests were carried out1 hour after removal from the drying oven).

    ______________________________________                                        Layer thickness          36 μm                                             Pendulum hardness 1 hour after drying                                                                  70 sec                                               after 24 hours           77 sec                                               Resistance to premium gasoline and xylene                                                              no marking,                                          (duration of exposure 5 minutes in each case)                                                          no softening                                         ______________________________________                                    

EXAMPLE 6

Formulation of a white top coat

    ______________________________________                                        Acrylate resin            38.6 parts                                          Hexakis-(methoxymethyl)-melamine                                                                         7.3 parts                                          White tinting paste P3    29.4 parts                                          Butyl acetate              5.9 parts                                          Butanol                   15.0 parts                                          Commercially available silicone oil (5%)                                                                 1.0 part                                           p-toluenesulfonic acid (40%)                                                                             2.8 parts                                          ______________________________________                                    

Adjustment diluent

xylene (18 sec DIN 4)

With forced drying (30 minutes at 60° C.), the following property levelis reached (unless otherwise stated, the exposure tests were carried out1 hour after removal from the drying oven).

    ______________________________________                                        Layer thickness           33 μm                                            Pendulum hardness 1 hour after drying                                                                   85 sec                                              after 24 hours            98 sec                                              after 14 days            155 sec                                              Resistance to premium gasoline and xylene                                                              no marking,                                          (duration of exposure 5 minutes in each case)                                                          no softening                                         ______________________________________                                    

EXAMPLE 7

Formulation of a clear coating

    ______________________________________                                        Acrylate resin            68.1 parts                                          Hexakis-(methoxymethyl)-melamine                                                                        10.2 parts                                          Xylene                    13.2 parts                                          Commercially available silicone oil (5%)                                                                 1.0 part                                           Pyridine salt of p-toluenesulfonic acid                                       (20%)                      7.5 parts                                          ______________________________________                                    

Adjustment diluent

xylene (18 sec DIN 4)

With forced drying (30 minutes at 60° C.), the following property levelis reached (unless otherwise stated the exposure tests were carried out1 hour after removal from the drying oven).

    ______________________________________                                                               Clear coating                                          ______________________________________                                        Layer thickness           32 μm                                            Pendulum hardness 1 hour after drying                                                                   95 sec                                              after 48 hours           111 sec                                              Resistance to premium gasoline and xylene                                                              no marking,                                          (duration of exposure 5 minutes in each case)                                                          no softening                                         Sticking test (1 hour stressed with adhesive                                                           no marking                                           tape:)                                                                        ______________________________________                                    

EXAMPLE 8

Formulation of a white top coat

    ______________________________________                                        Acrylate resin VII        42.0 parts                                          Hexakis-(methoxymethyl)-melamine                                                                         7.7 parts                                          White tinting paste P3    30.8 parts                                          Butanol                   15.6 parts                                          Commercially available silicone oil (5%)                                                                 1.0 part                                           p-toluenesulfonic acid (40%)                                                                             2.9 parts                                          ______________________________________                                    

Adjustment diluent

xylene (18 sec DIN 4)

With forced drying (30 minutes at 60° C.), the following property levelis reached (unless otherwise stated, the exposure tests were carried out1 hour after removal from the drying oven):

    ______________________________________                                        Layer thickness          32 μm                                             Pendulum hardness 1 hour after drying                                                                  81 sec                                               after 6 days             87 sec                                               Resistance to premium gasoline and xylene                                                              slight mark-                                         (duration of exposure 5 minutes in each case)                                                          ing                                                  Afier 48 hours           no marking                                                                    no softening                                         ______________________________________                                    

EXAMPLE 9

Formulation of a red top coat

    ______________________________________                                        Acrylate resin III       29.7 parts                                           Polyisocyanate           26.5 parts                                           (75%, triisocyanate from trimethylol-                                         propane with 3 mol of toluylene diiso-                                        cyanate, in ethyl acetate)                                                    Red tinting paste        25.0 parts                                           Butyl acetate            18.75 parts                                          Ethylene diamine          0.05 part                                           (10% in isopropanol)                                                          propanol)(sic)           100.0 parts                                          ______________________________________                                    

EXAMPLE 10

Formulation of a green top coat

    ______________________________________                                        Acrylate resin I         40.9 parts                                           Polyisocyanate           18.3 parts                                           (75%, triisocyanate from trimethylol-                                         propane with 3 mol of toluylene                                               diisocyanate, in ethyl acetate)                                               Green tinting paste      31.3 parts                                           Butyl acetate             9.4 parts                                           Ethylenediamine           0.1 part                                            (10% in isopropanol)                                                                                   100.0 parts                                          ______________________________________                                    

With forced drying (30 minutes at 60° C.), the following property levelis reached:

    ______________________________________                                                       Example 9 Example 10                                           ______________________________________                                        Layer thickness   40 μm    42 μm                                        Pendulum hardness                                                             6 hours after removal                                                                           53 sec      63 sec                                          24 hours after removal                                                                         137 sec     126 sec                                          from the drying oven                                                          Resistance to premium gaso-                                                                    no marking, no marking,                                      line and xylene (5 minutes                                                                     no softening                                                                              no softening                                     exposure in each case, 6 hours                                                after removal from the drying                                                 oven)                                                                         ______________________________________                                    

EXAMPLE 11

Formulation of a green top coat

    ______________________________________                                        Acrylate resin I       45.8    parts                                          Polyisocyanate         13.4    parts                                          (Triisocyanate from 3 mol of                                                  hexamethylene diisocyanate,                                                   trimerized, 90% in 1:1 butyl                                                  aceate/solvent naphtha)                                                       Green tinting paste    31.2    parts                                          Butyl acetate          9.52    parts                                          Ethylene diamine       0.08    part                                           (10% in isopropanol)                                                                                 100.00  parts                                          ______________________________________                                    

With forced drying (20 minutes at 120° C.), the following property levelis reached:

    ______________________________________                                        Layer thickness        40 μm                                               Pendulum hardness                                                             6 hours after removal  90 sec                                                 from the drying oven                                                          24 hours after removal                                                                              125 sec                                                 from the drying oven                                                          Resistance to premium gasoline                                                                      no marking                                              (5 minutes exposure, 6 hours                                                                        no softening                                            after removal from the drying                                                 oven)                                                                         Resistance to xylene, very slight                                             5 minutes exposure in each case                                                                     marking, very                                           6 hours after removal slight soften-                                          from the drying oven  ing;                                                    24 hours after removal                                                                              no marking,                                             from the drying oven  no softening                                            ______________________________________                                    

Pot life in a DIN 4 flow cup, rise from 20 seconds to 52 seconds in 24hours.

The acrylate resins I and III are examined by photocorrelationspectroscopy for a content of microgel particles. The result of theexamination is that there is no analytical indication of a microgelcontent. The resin solutions were examined by means of a Coulter Model N4 sub-micron partical (sic) analyzer of Curtin Matheson Scientific Inc.,Detroit, Mich., USA.

We claim:
 1. A hydroxylic acrylate copolymer comprising aprecrosslinked, ungelled reaction product ofabout 10 to about 60 percentof a hydroxyalkyl acrylate or methacrylate monomer (a¹) having from 2 to14 carbons in the hydroxyalkyl group; about 5 to about 20 percent of anunconjugated diolefinic monomer (a²), the olefinic groups being at thetwo termini of the monomer; about 15 to about 82% of a monoolefinicmonomer (a³) selected from the group consisting of styrene, vinyltoluene, acrylic acid, methacrylic acid and the alkyl, alkoxyethyl oraryloxyethyl ester of acrylic acid, methacrylic acid, maleic acid orfumaric acid; wherein all percentages are by weight relative to theweight of the copolymer and said copolymer is dissolvable in a saturatedorganic ester solvent, produces a viscosity of about 0.4 to about 10dPas when dissolved in an alkyl acetate solvent at a solids content ofabout 50 percent by weight, and exhibits no microgel content insolution.
 2. The copolymer according to claim 1 wherein monomer (a¹) isfrom about 15 to about 60 percent by weight, monomer (a²) is from about5 to about 20 percent by weight, and monomer (a³) from about 40 to about70 percent by weight.
 3. The copolymer according to claim 1 wherein themonomer (a²) has the general formula

    CH.sub.2 ═CRC(O)X(CH.sub.2).sub.n XC(O)CR═CH.sub.2

R being H or CH₃ ; X being O, NH or S; and n being an integer from 2 to8.
 4. A copolymer according to claim 3 wherein monomer (a²) is thereaction product of an unsaturated carboxylic acid and glycidyl acrylateor glycidyl methacrylate, or mixtures thereof.
 5. A copolymer accordingto claim 2 wherein monomer (a²) is the ester reaction product of anolefinic alcohol and a polycarboxylic acid or an unsaturatedmonocarboxylic acid.
 6. A copolymer according to claim 2 wherein themonomer (a²) is the reaction product of polyiscyanate and an olefinicalcohol or amine compound.
 7. A copolymer according to claim 2 whereinthe monomer (a²) is a diester formed by reacting diol selected from thegroup consisting of polyethylene glycol, polypropylene glycol, andmixtures thereof, with an olefinic carboxylic acid selected from thegroup consisting of acrylic acid, methacrylic acid, and mixturesthereof, said monomer (a²) having a mean molecular weight of less than1500.
 8. A copolymer according to claim 7 wherein said monomer (a²) hasa mean molecular weight of less than
 1000. 9. A copolymer according toclaim 1 wherein monomer (a¹) contains a primary hydroxyl group.
 10. Acopolymer according to claim 1 wherein monomer (a¹) is at leastpartially comprised of the reaction product of 2 mol ofepsilon-caprolactone and 1 mol of hydroxyethyl acrylate or hydroxyethylmethacrylate.
 11. A copolymer according to claim 1 wherein monomer (a¹)is comprised of up to 75% by weight of a hydroxyalkyl acrylate ormethacrylate having a secondary hydroxyl group.
 12. A copolymeraccording to claim 1 wherein monomer a¹ is a reaction product ofglycidyl ester of a carboxylic acid having a tertiary alpha carbon atomand acrylic acid, methacrylic acid, or mixtures thereof.
 13. Aprecrosslinked, ungelled copolymer according to claim 1, produced by theprocess comprising:combining monomers a¹, a² and a³ at said relativeweight percents, polymerization initiator, at least 0.5 percent byweight of total solids of a polymerization regulator, and an inertorganic solvent to form a mixture, the total monomeric a¹, a² and a³content in the mixture being from about 40 to about 65 percent by weightrelative to the total weight of the mixture; and heating the mixture ofabout 80° C. to about 130° C. for a period of time sufficient tocomplete polymerization and product the copolymer.
 14. The copolymerproduced according to claim 13 wherein said initiator is selected fromthe group consisting of a peroxy ester compound and an azo compound. 15.The copolymer produced according to claim 13 wherein said azo compoundis azobisisobutyronitrile.
 16. The copolymers produced according toclaim 13 wherein the heating is carried out at a temperature of about90°-120° C.
 17. The copolymer produced according to claim 13 wherein thepolymerization regulator comprises at least about 2.5% by weight of thereactants.
 18. The copolymer produced according to claim 13 wherein thepolymerization regulator is a mercapto-containing compound.
 19. Thecopolymer produced according to claim 18 wherein the polymerizationregulator is mercaptoethanol.
 20. The copolymer produced according toclaim 13 wherein the percentage of monomer (a¹) is from about 15 to 60percent, the percentage of monomer (a²) is from about 5 to about 20percent, and the percentage of monomer (a³) is from about 40 to about 70percent.